BONES OF THE WING. 143 



cavity receiving it. The ulna is always stronger than the 

 radius; but both are long, slender, and nearly straight 

 bones, so articulated together as to admit of scarcely any 

 rotation which adds to the resisting power of the wino* 

 in the action of flight. The upper part of the ulna, or 

 "olecranon," is short. In the tendon attached to it, a 

 separate ossicle is developed in the swift, and two such 

 bones in the penguin. The ulna is often impressed by 

 the insertions of the great quill-feathers of the wing. 



The bones of the hand are very long and narrow, with 

 the exception of the two distinct or unanchylosed carpal 

 bones ; these are so wedged in between the antibrachium, 

 54, 55, and the metacarpus, 57, as to limit the motions of 

 the hand to abduction and adduction, or those necessary 

 for folding up and spreading out the wing. The hand is 

 thus fixed in a state of pronation ; all power of flexion, 

 extension, and rotation is removed from the wrist-joint ; 

 so that the wing strikes firmly, and with the full force of 

 the depressed muscles, upon the resisting air. The part 

 of the hand numbered 57 in Fig. 24 includes the meta- 

 carpal bones of the digits answering to the second, third, 

 and fourth of the pentadactyle members, which are con- 

 fluent at their proximal ends with each other, and with 

 the " OS magnum," one of the carpal bones, now forming 

 the convex base of the middle metacarpal. This meta- 

 carpal, and that answering to the " fourth" digit, are of 

 equal length, and are also confluent at their distal ends ; 

 but the middle or " third" metacarpal is much the strong- 

 est. That answering to the "second" digit, ?V, is very 

 short, and like a mere process from the third ; it supports 

 two short phalanges in the swan. The third metacarpal 

 supports three phalanges, m, the fourth a single phalanx, 

 iv. All these are wrapped up in a sheath of integument, 



